The refrigeration industry has been working for the past few decades to find replacement refrigerants for existing refrigerants including ozone-depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). These existing refrigerants are being phased out as a result of the Montreal Protocol. The solution for most refrigerant producers has been the commercialization of hydrofluorocarbon (HFC) refrigerants. Some new HFC refrigerants have zero ozone depletion potential and are therefore not currently subject to the Montreal Protocol phase-out.
Further environmental regulations, however, may ultimately cause global phase out of some of these HFC refrigerants due to their global warming potential (GWP). Currently, industry is facing regulations relating to GWPs for refrigerants used in mobile air-conditioning systems. If the regulations are more broadly applied in the future, for instance to stationary air conditioning and refrigeration systems, an even greater need will be felt for refrigerants that can be used in all areas of the refrigeration and air-conditioning industry. Uncertainty as to the ultimate regulatory requirements relative to GWP has forced the industry to consider multiple candidate compounds and mixtures.
Previously-proposed replacement refrigerants for HFC refrigerants and refrigerant blends include HFC-152a, pure hydrocarbons, such as butane or propane, or “natural” refrigerants, such as CO2. Each of these suggested replacements is associated with numerous problems, including toxicity, flammability, and low energy efficiency, and may further require major equipment design modifications. New replacements are also being proposed for the refrigerants R-22, R-134a, R-404A, R-507, R-407A, R-407C, R-407F, and R-410A, among others. The uncertainty regarding future GWP regulatory requirements has caused the industry to look for compounds and mixtures that balance the need for low GWP and non-flammability, as well as the need to match existing system performance parameters.